Hydraulic mechanism



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Patented Nov. 21, 1950 HYDRAULIC MECHANISM Max A. Mathys, Detroit,Mich., assignor to Ex- Cell-O Corporation, Detroit, Mich., a corporationof Michigan Application January 8, 1944, Serial No. 517,541

18 Claims. 1

' The present invention pertains to a novel hydraulic mechanism, andmore particularly to one which is especially suited for efiecting, inthe course of its cycle of operation, an accurately controlledstep-by-step motion of a driven member, such as may be employed, forexample, in accomplishing the infeed of the wheel slide of a traversegrinder.

The general aim of the present invention is to provide a hydraulicmechanism or actuating system of the general type indicated which isfully automatic and which is characterized not only by its precision ofoperation but also by its versatility of adjustment to accommodatedifferent operating requirements.

More particularly, one object is to provide such a system in which anovel arrangement is provided for adjustably and precisely determiningthe limits of the last step in a step-by-step advance, therebyespecially accommodating the same for use in a machine where such laststep is used in making a finish pass or cut in bringing a work pieceexactly to size.

Another object is to provide in a system employing withdrawal of meteredincrements of fiuid from a piston and cylinder type actuator ineffecting step-by-step advance, a novel arrangement for eiiecting anautomatic reversal of the actuator after completion of the step-by-stepadvance.

. Another object is to provide in a system employing withdrawalfrom anactuator of metered increments of fluid to effect the advance of suchactuator, a novel arrangement'for safeguarding the 'metering-out circuitagainst leakage.

,Another object is to provide in a hydraulic system, a novel arrangementfor insuring the precision stoppage of an actuator in a finalpreselectable position therefor and which arrangement operates with thesame fidelity in duplicating the final position of the actuator at theterable starting point, such arrangement being adapted for employmenteither with or without step-by-step advance of the member in at least aportion of a cycle of reciprocation therefor.

Further objects and advantages of the invention will become apparent asthe following description proceeds, taken in connection with theaccompanying drawings in which:

Figure 1 is a generally schematic perspective view of the major elementsof a traverse grinding machine having applied to its wheel slide a,hydraulic actuating system embodying the present invention.

Figs. 2 to 5 are simplified hydraulic diagrams of the actuating system,Fig. 2 indicating the flow of fluid during rapid approach of the slide,Figs. 3 and 4 indicating the flow of fluid during two successive stepsin the step-by-step forward feed movement of the slide, and Fig. 5indicating the fiow of fluid during the rapid return motion of theslide.

Figs. 6, 7 and 8 are successive stop motion views of the stop mechanismin the end of the actuating cylinder which serves to determineadjustably the length of the last step of advance of the actuator, theparts being shown partially in ion-- gitudinal section.

Figs. 9 to 12 are simplified hydraulic diagrams of the control portionof the hydraulic circuit, illustrating the successive conditions offluid flow in the same incident, respectively, to rapid approach,completion of the next to the last step and last step of thestep-by-step advance of the actuator, and to rapid return movement ofthe same.

Fig. 13 is a complete hydraulic diagram of the system, illustrating insection the preferred form of the various valves.

While the invention is susceptible of various modifications andalternative constructions, I

have shown in the drawings and will herein describe in detail thepreferred embodiment, but it is to be understood that I do not therebyintend to limit the invention to the specific form disclosed, but intendto cover all modifications and alternative constructions falling withinthe spirit and scope of the invention as expressed in the appendedclaims.

Referring more particularly to the drawings, in Fig. 1 has been showngenerally schematically the major elements of a traverse grindingmachine, such a machine being simply representative of the type ofinstallation in which hydraulic systems embodying the present inventionare especially suited for use. Such major therefrom.

elements include a table I adapted to carry and reciprocate axially arevolving Work piece 8 which is to be ground. On a wheel slide I is arevoluble grinding wheel 9 engageable with the Work 8. The hereindisclosed hydraulic system is adapted to effect the so-called infeed ofthe wheel slide, in a direction transaxially of the work.

In brief, the preferred controls-for'the wheel slide I6 are such thatupon starting, an automatic cycle is executed which consists of a rapidapproach of the slide in to working position, thereafter successivesteps of advance for the slide alternated with passes of thework by thereciprocating table 7, and a rapid return.of.the.1slide to startingposition after it has completed its step-by-step advance to apredetermined depth of cut.

In the illustrated embodiment, movement of the slide II] is effected bythe coaction of a first fluid typeactuator, consisting of a cylinder llaanddiiierential'piston I2, witha second fluid actuator, ormoreijspecifically, a. fluid. plunger devicenthe latter consistin of acylinder Ila and plung' er III. Boththe cylinders TI Ia and Ho. aresftationarilymounted, as, for example, in the base of. t h'efr'na'chinef.Theslide. IE! is in efiectfforced constantly againstthepiston I2 bytheplunger .II. .To .advancethe slide; IE3, fiuidis withdrawn from-thecylinder l 2a at-h the forward face .of the ,pisto'nsokthatthe pistonI-Zactsas a, retreating n -abutment for-limiting the advance of the slideunder'the constant urge of the plungerII. To cause theslide-toreturmrthe application of pres- .surelfluidtothe cylinder IZaisreversed, the plunger II being overpowered. The length of travelfcrtheslide Iaisthus determined bythe fixed-stroke of the-actuatorpiston. I2, but the .startingpoint can be adjustably varied by ad-.-iusting the length -of=the coupling between the actuator I2, Ma andslide, the plunger I Iserving ,thr-Q l hQut-such range of =-adjustmentto retain .theyslide and actuator engaged,

As-,to vthe:particular coupling set-up shown inIEigglgtheractuatorpiston I2. has at its outerend an abutment rollerIzflil bearing against the curved face of a transverse link IOI. Theends of .the link tItIlI are yoke-shaped, the righthand end beingvpivotedasiindicated'at I02 onasleeve I03 whichris journaledupon ashaftdfldythe sleeve beingrestrained against axial movement withrespect-tothe shaft. The shaft itself is threaded ewithin a nut I05,the'latter being held against 'rotation'by a-stationary spline key I06entering a longitudinal slot in the nut. Bearing against the outer endface of the nut 1.05 is an adjustable abutment: I'filffixed to the slideII). -By revolving the shaft Hi l the same is screwed into or out ofthe.'nut.Iil5,-thus adjusting the position of the islidez-iillrelativeto its actuator I2, I2a. In this -way.the.locati-on of the slide IE]relative to the uWOl'k 8 may-be'adjusted atwill even though its actuatorI2, IZa has a stroke of fixed'length.

The plunger I I serves to urge the slide In con- :stantlyinaa: forwarddirection to retain the slide abutment I 0? constantly in engagementwith the end of the nut Hi5. For this purposethe plunger Ii is arrangedto bear against theface-of a bracket. I88 rigid with the slide IO-anddepending The-usual sizewheel I69 serves to adjust the shaft Iiinvithinthe nut I65. This wheel is connected through gears I Hi with a gear I II splined 'on the shaft I04 so that turning of the wheel I09 a'diuststhe slide I0 either forwardly or-rear- .the rod I I5 being pivoted tothe lefthand end of the latter link. With such an arrangement, as thetableadvances the sine bar II2 shifts the member H3, thereby causing thelink IUI to --"fulcrum about-the. roller I60 so that the slide I0 isadvancedin timed relation with the axis of the work'to produce a taperedsurface on the latter.

Power circuits of the system The preferred hydraulic circuit embodyingthe actuator, I 2, l2a and plunger I I isshown in full inEi'gfBfbut, itsintricacies will best be understood. after. a preliminary consideration.of certainjsirnplified or partial'showings of the circuit inflordefthatthe general plan of operationmay be clear. For that purpose the fluidflow for the actuator or power. circuits .proper has. been diagrammedin'Figs; 2' to dim successive cycle steps, and thefluld flow for thecontrol circuits ofithe systemjhas'. been similarly diagrammed in Figs.9 tol2. Reference may be first made to Fig. 2. As there, shown, fluidsuch as .oilis supplied under pressure. from a suitable constantpressure source such, for example, as a constant deliverypumpP equippedwith a conventional spring loaded working pressure relief valve V.Thejpump draws fluid 'fiomareservoir R' and delivers'the'same underpressureflthe relief 'valve'serving to return such "excess fluid tothereservoir as may be required toimairitain the pump delivery pressuresubstantially-constant-at a'valuev determined by the adjustment of'itherelief valve. Pressure fluid from the pump- P is delivered throughpressure line I8 directly and constantly-to'the outer end of the plungerI I andal's'p to a starting. and reversing valve-Fig 3. The latter is atwo- -position valve having forward and reverse positions and when inits, forward position it dispatches'fiuidfrom the pressure line"I81through '1ine23 tothe cylinder fz'affdr advancing the piston [2. InFigS. 2130.5

and Q to 12 the heavy black shading indicates "fluid underpre'ssuredirectly. from the pump while a dottedlin'e" in the conduitindicates'fluid, at an xliaust pressure. 'iIn.E ,gs.f3" and 4 the broken--heavy'lines'incertain fthe conduits indicate fluid trappedin the,metering circuit and. which is reta'inedfunder pressure substantiallyequal to the pump discharge pressure, for a purpose which will ater appar- ?To institute .acycleof operation, rapid advance of the .slidellljjisinitiated by shifting thevalve 'f3tojits, forwardposition(indicated in Fig. 2),

whereupon 'itdispatches pressure fluid from line {Bf-through. line 23.to the actuator. cylinder I2a and causesllfiuid to becexhausteld fromtheoppos1te-end of such cylinder" through line 24 and thence throughline 25 and aimed control valve '15) back to; the reservoirRthroughexhaust line .I 9 ='If desired, a conventional spring loadedback pressure valve I9a may be interposed in the er the plunger beingreduced in diameter to. pre:-

sent a cross-section one-half that of the inner end. Pressure from thepressure line [8 is applied tothe face 28 of the shoulder on the plungerbetween its large and small-portion and through -a line 29 to the'innerend 3|] of the plunger.

Since the area at 3B is twice as large as that of theshoulder 28, theplunger is yieldably thrust outward against a bushing 3| fixed in thevalve casing 21. In such position of the valve, the lin is connectedthrough an internal bore 34 and cross passages 33 in the punger toexhaust line IQ for the free exhaust of fluid from the line 25 to effectrapid'approach of the slide as noted above. A separate plunger 14 in thelower end of the valve casing serves to thrust the main plunger 26outward upon application of pressure fluid in a manner hereinafterdescribed to set the plunger 26 in its projected position. Once theplunger 26 is so projected it will remain, due to the differentialpressure action on it, until mechanically thrust in a short distance,whereupon fluid resistanceto such thrust is relieved so that the.plunger can. continue its retraction without impediment.

plunger 26 of the feed valve l5 (Fig. 3). Shift- 0 .ing of this valveplunger 26 causes the valve I5 to interrupt the exhaust of fluid fromthe cylinder l2a through line [9 and to direct the fluid from suchcylinder through an arrangement which meters the fluid out of thecylinder in predeter- .mined. small increments. Each increment of fluidso metered out permits the piston l2 to advance a corresponding fixeddistance.

When the dog thrusts the valve plunger 26 inward, the exhaust line 19 isconnected through the passage 29 to the rear end 30 of the plunger sothat the latter can complete its inward movement without impediment.Such inward shift of the plunger 26 cuts off the connection to exhaustfrom the line 25 and blocks the latter (seeFig. 13). A separate slidingplunger 14 limits the inward movement of the main valve plunger 26.

The mechanism for metering out increments of fluid from the cylinder l2aconsists of a plunger l6 slidable within a cylinder l6a provided with anadjustable stop pin 38 at one end thereof for limiting the path oftravel of the plunger. A micrometer head (see Fig. 13) on the stop pin38 servesto adjust its position. Cooperating with the metering plungerl6. and connected theretoby lines 36, 3'! is a reversing valve 14 whichserves to direct fluid to alternate ends of the plunger Hi from theoutlet of the actuator cylinder l2a and in each case to exhaust theopposite end of cylinder lGa to line [9. The valve i4 is fluid operatedin timed relation with the table I in such manner that the valve I4 isactuated upon each stroke of table movement. For this purpose areversing pilot valve 1a (Fig. 3) is actuated by the table 1 to directpressure fluid through alternate ones of pilot lines or conductors 2|,22 and exhaust the other, thereby alternating the position of theplunger of valve l4.

Since the shifting of the valve l5 to institute feed blocks the line 25,as heretofore described, so that fiuidfrom the cylinder l2a' can nolonger go to the exhaust line, l9, it is, instead, forced through thevalve l4 into one end or the other of the metering cylinder 16c asdetermined by G the position of the valve l4. Under theconditions shownin Fig. 3, fluid is forced out of the-actuator cylinder lZa through theline 24 and is directed by the valve l4 into the lefthand end of themetering cylinder I611, thus forcing the metering plunger 16 to theright to -the limit position determined by the adjustable stop 38.Simultaneously, valve I4 exhausts the opposite end of the meteringcylinder I6a by connecting it to exhaust line l9. An increment of fluidis thus displaced from the actuator cylinder l2a which is equal to thevolume of the space vacated by the plunger [5 in its shift, and theactuator piston l2 together with the slide in is advanced acorresponding fixed distance. Upon the completion of the shift of themetering plunger IE to the right, the slide [0 comes to rest, since nofurther fluid can be displaced from the actuator cylinder l2a.

Upon the completion of the next stroke of the work supporting table Ithe pilot valve la is actuated thereby to reverse the pressureconditions in the pilot lines 2!, 22 (Fig. 4) so that pressure isapplied through line 2| and fluid exhausted through line 22, thusshifting the reversing valve id. Such shift of the valve I4 directsfluid into the righthand end of the metering cylinder Mia and connectsthe lefthand end .to exhaust through line l9. Thereupon the meteringplunger [6 is displaced to the left, a corresponding amount of fluidbeing received from the actuator cylinder l2a so that the slide It] canadvance another step. In this same general manner the metering plungeri6 is shuttled back and forth with one stroke of the plunger upon thecompletion of each stroke of the work supporting table I, so that theslide it is advanced one step after each stroke of the table.

Provision is also made for instituting drive of the work spindle as anincident to shift of the valve'l5 at the completion of rapid approach.For that purpose the valve l5 connects line 29b to exhaust line l9,thereby exhausting fluid from a cylinder 290 so that a spring-urgedplunger 29d moves downward to close its associated switch contacts 29c.Closure of these contacts may be used to complete the energizing circuitfor the electric drive motor (not shown) which revolves the work piece8.

- Upon completion of the step-by-step feeding advance of the slide l5,its motion is reversed through the medium of an automatic controlarrangement hereinafter described, and it is automatically returned tostarting position. During such rapid return movement of the slide (seeFig. 5) the valve I3 is in its reverse position, while the valve i5 isrestored to the position which it occupied during the rapid approachmovement illustrated in Fig. 2. The control circuits for operating thevalves I3 and I5 to effect reversal are hereinafter detailed inconnection with Figs. 9 to 13. Incidentally, it will be noted that thespringurged dog 35 rides freely over the plunger 26 during its returnmovement and consequently does not actuate the latter during suchreturn. For the rapid return movement in question, pressure fluid fromthe line [8 (Fig. 5) is dispatched by the valve 3 to theouter orlefthand side of the piston l2 through line 24 and fluid is exhaustedfrom the righthand end of the actuator cylinder through line 23, valvel3, line 25, valve 15, and thence through exhaust line l9 back to thereservoir. Although the application of pressure fluid to the plunger His continued during such return movement, the greater area of the At h'eii f. mail-earn fiv fi j it co mesto i'e'st upon abutment cif thepiston 12 against t .rig th li e d. cubetilinien'ld- D ri eth iwmpf t eli eihs spinql ent-ita sw iehw iap ar Q ened hr' ressii efluid suppliedfromthepressure line l8 through the "valve I5 and line 29b.

Readily adjustable step-by-step motion of the As will be evident Jis-limited to an amount proportionate to the shift ofthe'plunge r It.Such plunger shift can be readilyadjusted by changing its stroke throughithe use'ofthe stoppin 38.

Control of last feed-step Special provision is made 'for adjustablycontrolling" the length or the'last step in the stepby step'adiiance ofthe slide Ii]; Such adjustment is quite'independent Of the length of thepreceding-steps which, as'heretofore explained, are determined by thesetting of the adjustable stop p'in 38. Precise and a'ccurate-control'ofthe length of the last step of advance is especiall desirable in thatthe-length of such step commonly determines the amount'of' metal whichis to be removed during the last or finishing'passof the work past thetool. It is requisite" not only that thelength of this step should beaccurately controlled, but alsothat thefinal position of the slidebe-determined with extreme certainty as Well as exactitude since thatposition determines the final size of the work.-

In accomplishing such control of thelast step I otadvance of the slide,a movable stop in the form of a bushing H is interposed in the path ofadvance of the piston l2 (see Figs. 2, and 6 to This stop it interceptstheadvance of the piston at the end of the next to the last step, andfor the final step thestop I I is permitted to retreat an accuratelydetermined distance. The stopbushing I7 is slidable axially within abore i1 a coaxial with and openinginto the end of the cylinder lzcoppositethe large face of the piston (2.. .Qutward movement of the stopbushin'g- I] is limited by the seating of its outer end against anabutment. surface 48- on the end wall o f the bore lla; while movementof the bushing in an opposite or inward direction toward the piston I 2is limitedby engagement of projections 5| with mating projections 49a ona 1 1. iikey di li e ndw s W t a ta n.- .irhws W A qr er a iu ne w .3 isthreaded on the plug 49 and held against endf P ait? qiu t sk p fl 9 w21 42 mm el is isa .ni i by. a e i th se q pel e ii t ab imen s tiaqe .4and lp i qii s. 42 eiihailihe l n theimrmfliedsix kel gr the p. buhing-J1 .i r sbandin ly a lst d. i.

,.,\;. .t e o ter nd 9f thestop.bushin .l a c nh .2. s. provid dut wwhicre sure. fl i is. sup,- n i din mann r, er in it rs escribed s tha thepr ss r f su ...fl d,: u m n e by aispr ne 46,..n rmall ,.urg s the. opbushi ar h -pistonl2 whose mo tion it intercepts. {Fig. jfi),

vSlidable axially within the bushing l isjthe stem 53a" of a disk-shapedvalveelement ,5?! which seats on" an annular seat 58 formedvon the outerface'of the bushing. The valve element is urged into "seated position by.a' compression spring, interposed between the bottomhof a bore'iin theplug 49 and theo'uter face-of the'valvediskfl. .Whenthe valve element 53is unseated',-pressufe fluid" passes by "the same and out a" 'passa'ige59 from the chamber 52 to condition .the"contro1 circuits hereinafterdescribed so that upon the next stroke of the work table I the'chambr'52 wi 11'-be=exhausted, thereby permitting the actuator piston rzj toro ethe bushing [1 to the'left'and againstjtheabutmeht' face 48 for thelast step of advance'of the actuator piston; i

Asjthe actuator piston approaches the stop "fig n the parts occupy therelative "p" ishown Fig; 6, the'biishin bing' yil'd any urgedfiowa rdthe actuator piston by the t awamnes a-n imiw em'aw b 525-. n'i d u efqili m tg j 1 5 step lof' ad nee-of the ectuator piston f2" the litter lts .ans .I IdfiLfii' W -Idi. plunger 5 3a' ther'by unseatingjtlfefvjalvec vmmodat is i hg qtionqih ilfunsir fita'is ens on d' pi n a't i, t itan' i chlb d t e f ce D? .1 sla h n t in a h en v menace thelastistepoffadvance of the actuator piston .thepartsfcoiiieito restin' thepositi; hown in File 7., n thella tterpositioiijthestopbushingjf is silltlii usfito thefright;intercepting the'p st l2" in thedesired'position for institutiolrf'o laet stepior the latter. Eventhough th yalv'e for th 'lasti'stepiof. advanc s'tillfthe 'pressiire"hasnot heri' relieved in hamber 152' so: the; bi i isi" is still df f i s ue. are" it matin'g'p'rojectionflgi As her t ielcb' n etiorl or 'th extstroke; of the work table results-in the :ekhaust' of 'fiu'id from thechamber 52; whereupon the actuator vpistc'yni.it s free dtothrust thestopbushirig" I'Lt'o the left against the abutmentfaces' 48 for thelast: Step of; advance of the actuator piston. In enti y th r id-a u ent48 .li 'ii ve r' d fi 'r' n .ti final position of thlactuatorpiston Igana, a simple s in t i ei c p he a vs mm knob 56a determines the lengthof such last step of piston advance.

A'zztoifiittic ri'ieisdl O ni 'o i th flv v 53 a' ide 'n b i in thecourse of the next to the last step of advance for ;the actuator pistonnot only conditions the circuit for retreat or -the stop bushing] 1. asindica ted, but in addition s i s ,9 the C'i cuitsfofiim interrelatedcontrol valves which takes place,

preceding and as an incident to reversal of the slide I is showngenerally diagrammatically in Figs. 9 to 12. Fig. '9 exemplifies theconditions prevailing during rapid approach movement of the slide. Fig.10 exemplifies the circuit conditions at the completion of the next tothe last step of advance, thus matching Fig. 7; while Fig. 11 shows thecircuit conditions prevailing after the last step of advance of theslide, but during the succeeding stroke of the work table, thus matchingFig. 8. Finally, Fig. 12 shows the fluid flow in the control circuitafter the last stroke of the work table.

Included in the portion of the circuit to be considered in connectionwith reversal and the delayed action control thereof are, in addition tothe reversing valve l3 and feed valve l5 already identified, four pilotvalves 54, 55, 55 (Figs. 9 to 12) and 51 (Figs. 11 and 12). Each of theadditional valves noted is fluid operated, all being of the slidingplunger type, and of them the valves 54,55 and 51 are two-positionvalves, while the valve 55 is of the three-position type, having anormally centered plunger.

In brief, the arrangement is such that the pilot valve 54 is shifted inresponse to completion of the next to the last infeed step of theactuatorpiston I2. Thereafter the pilot valves 55, 55 coact to delaywithdrawal of the stop bushing until after'one further stroke of thework table i and to delay operation of the valve 51 (which controls thereversing valve |3) until after two further strokes of the work table.

the same irrespective of which of the intermittently reversed lines 2|,22 happens to be connected to pressure at the time When'the next to thelast step of infeed is completed.

Attention may now be given to the successive conditions of fluid flowdiagrammed in Figs. 9

to .12. During rapid approach of the actuator piston l2 (Fig. 9) thefeed valve l5 dispatchesfluid from the pressure line l8 through a branchconduit 29, to the valve 54 so that the latter is shifted to the left.With the valve 54 in the latter position, pressure fluid from the lineI8 passes through an annular peripheral groove 65?;

in valve 5 1 (see Fig. 13) and thence through the branched conduits 60to the chambers 50a at opposite ends of the valve 55, thereby centeringthe latter.

the line it through line 55 to the chamber 53- located at the outer faceof the stop bushing l? as heretofore described. The pressure fluid thussupplied to the chamber 52 urges the stop bushing i! toward the actuatorpiston l2 in position to intercept the latter at the completion of'thenext to the last step of the step-by-step infeed which is to follow. Byconnections which will later The pilot valves are coordinated so thatthe action shall be Pressure fluid in the conduit 6|) also shifts thevalve 56 to the right, the right end of 10' appear (Fig. 13) pressurefluid in line 69 also shifts a valve 5'! to the right.

Upon the dog operation of the feed valve l5 to change from rapidapproach to step-by-step infeed movement in the manner heretoforedescribed, such shift of the valve l5 connect the line 29 to the exhaustline l9 and disconnects it from the pressure line I8. At-that point in'the cycle both ends of the valve 54 are thus connected to exhaust sothat it remains in the positicn to which it was shifted by the previousapplication of pressure shown in Fig. 9. At the end of the next to thelast step of infeed for the actuator piston l2, the valve 53 is, asheretofore explained, opened by contact of the piston l2 with the end ofthe valve stem 53a.

Such opening of the valve 53 directs pressure fluid from the line andchamber 52 into a" line 59 leading to one end of the pilot valve 54. Theopposite end of such valve 54 having been previously connected throughline 29] to exhaust, the valve 54 is shifted to the right. The

shift invalve 54 results in connecting line to pressure, to one of theends of the centralportion of the valve through the corresponding one oflines 6|, 62 and connection of another part of such central portion ofthe valve 55 to exhaust through the other one of lines BI, 52 and theother of the pair of lines 2|, 22."

, The central portion of the valve 55 is constructed in a manner suchthat application of pressure through the line 2| and exhaust throughline 22 causes it to shift to the right and, con

versely, application of pressure through line 22 and exhaust throughline 2| shifts the valve 55 to the left. But in either case, whether thevalve 55 is shifted right or'left, it connects to the exhausted one ofthe pair of lines 2|, 22, a

line 55'leading from the right end of the final collars or lands 53 andis disposed within a central chamber 54 in the valve housing. The lines5|, 52 open into the central chamber 6 at points spaced apart slightlymore than the spacing of the collars 63, whereas the line to the rightend of the valve 55 opens into the centerof the chamber of valve 55 andlines 68, 69

lead from spaced points in such chamber.

The cooperatin pilot valve 54'has an axial bore 54b in its plunger 54a,such borebeing'; always connected to exhaust line l9 by transversepassage 540 in the valve plunger. Such transverse passage 540 alsoregisters with'line' 52, as does a second transverse passage 54d withline 5!, so that both lines 6|, 62 are exhausted."

5|, 62, and chambers 6511 at the ends of valve 55 are connected toexhaust line l9: through line' 69.- a transverse bore Ste in-theplungerof valve Pressure fluid is dispatched from f 54, and the axial bore 54b.in the latter. Accordingly, should pressure be available in line 2| theplunger of valve. 55 is shifted to the right, while if pressure isavailable in line 22 such plunger is shifted to the left. Ineither casethe one of the lines having pressure in it is connected to thecorrespondin one of lines 68, 69 while the other or exhausted one oflines 2|, 22 is connected to line 65.

The net efiectof shifting the pilot valves 54 and 55 as just described(see Fig. is, as-

noted, to connect the right end of the third pilot valve 56, throughline 65, to the one of the lines 2|, 22 which is at the momentexhausted. That does not result in any shift of the valve 56, for itsright end was previously connected to exhaust through conduit 61 and anannular pee ripheral groove (see also Fig. 13) in the plunger 14b. Thelatter connection is, incidentally, interrupted by the shift of thevalve55. But the newly established connection to the valve 56 does insure'itsactuationupon the next succeeding reversal of pressure in the lines 2|,22. Accordingly, when the table I completes .its next stroke (i. e., forthe last roughing cut in the cycle of operation ofrthe grinding machine)the consequent reversal in pressure in the lines 2|, 22 causes the valve56' to be shifted to the left (Fig. 11)

Buildingup of undue pressure in the line 24 from the actuator cylinderis prevented after contact of the piston I2 with valve stem 530. byarrangingthe. pilot valve 54, when shifted to the right, to connect line24 to exhaust (Fig. 13). Thus a cross passage 90 in theplunger. of valve54connects line 24 to exhaustline I9 through the central bore 54b.

The first result of shifting the pilot valve 56 to the left is toestablish a connectionthrough it from the chamber 52- to exhaust so thatthestop I'I is-withdrawn to permit the final infeed step of the actuatorpiston I2 (Fig. 11). For thatpurpose the line 45.1eadingfrom the chamber52 is connected to the exhaust line I9 through an an nular peripheralgroove 56b in the plunger 56a of the-valve 56 (see Fig. 13).

A secondary result of shifting the pilot valve 56 is to establish aconnection for actuation of. the reversing valve 5'! upon completion ofthe next or final stroke of the work table I (Fig. 12'). At thecompletion of such final table stroke (i. e., for the final finishingcut on the. work in the cycle of the grinding machine) pressureconditions in the lines 2 I, 22 are again reversed (compare Figs. 11 and12). Accordingly, if line 2| istheone of the pair put under pressure atthat time, as is. the condition indicated in Fig. 12, pressure fluid issupplied from line 2 I, through valve 54, line 6|, valve 55 and line 68and valve 56 to a-line III leading through a valve 66 and line 8| totherighthand end of the valve 51, lines 68 and I0 being interconnectedthrough an annular peripheral groove 560 in the plunger of the valve 56(see Fig. 13). Thisshiftsthe plunger 51a of the valve 5T to the left,its left end being connectedtoexhaust through line 60 and valve 54.Similarly, if pressure happens tobe applied to line 22fat such time.pressure fluidwill also be supplied to line 16 with like result, butthis time through valve 54, 1ine.62, valve 55, and thence through line69 and the annular groove-56c'in valve 56 (Fig. 13).

Shiftingof thev valve 5'! to the left asdescribedl causesthevalvefl tobe Shifted/5011135 [reversin position and the feed valve I5 toberestored toits initial or rapidposition (Fig. 12).. Thuszvalve 51applies pressure from the pressure line I8 through the line 13 and achoke I2 to achamber at the upper end of the plunger of the valve I3 toforce the same downward. Pressure fluid is also supplied to a chamber atthelower end of the actuatingpiston 14 of the valve I5 to thrust theplunger 26 of this valve outward, such pressure fluid being appliedthrough line 13 and a choke I2 as Well as from the. pressure passage 19.

and a. choke 9| after the'valve I3 has shifted. The purpose of thechokes 12.and 9| is to make it possibl to supply line.'|3 via either thevalve 51 or I3. The valves I3 and I5 are thus conditioned for rapidreturn movement of the slide in the manner heretofore described inconnection with Fig. 5,

It will thus be seen that the stop I! is Withdrawn an the slide actuatorI2, I2a reversed in proper sequence, and all in carefully coordinatedtimed relation with the intermittent reversals of pressure and exhaustin lines 2 I, 22 occasioned by reciprocations of the Work table 1.

Manual control If desired, the machine ma be operated by manual controlof the advance of the slide I0 rather than with an automatic cycle ofsuccessive steps as described. Such operation is especially required forobtaining the initial setting on the size wheel I69, while setting themachine to a new work piece. In such manually controlled infeed'of theslide the size control wheel I69 (Fig. 1) is turned a desired distancefor each successive step. To'condition the machine for such manuallycontrolled operation, two valves ar utilized in addition to certain ofthose heretofore noted; namely, an automatic" feed disconnect valve 66and a size pick-up valve '81 (Fig. 13).

The'disconnect valve66isa simple manually operable twoposition rotaryvalve. When'inits automatic feed position shown in Fig. 13, itconnectsline Ill to line 8| for supply of pressure fluid for shifting the valve51 at the appropriate point in the cycle, as heretofore described.Turngrooves 92c, 92d and 92e in the plunger are interconnected by anaxial bore 92f in the plunger,

grooves 920 and 92dhaving the same spacing as portsfrom the lines 25 andI9.

Assuming the slide I0 is withdrawn its full distance, the machine isconditioned for manual operation by turning-thevalve 66 to connect line8| to exhaust. The valve I3 is then shifted man ually to its forwardposition, whereupon the slide advances rapidly, just as in the automaticcycle, until the valve Ifi'is-tripped. Then the operator pushesinvalve8], connecting line 25 to exhaust so that the-advance of the piston I2continues without interruption until it comes up against the stopbushing IT. The direction of travel for the table "I is reversedmanually. This will exhaust chamber 52 causing piston I2 to be shiftedto the maximum forward stop position. Either desired subsequentadvanceof the wheel slide It! forgrinding or location of the wheel slideat a desired finalstopped position maybe obtained byturning theslzewheelI69. If it is desired togrind automatically, after the size setting isthus established, valves 66 and I3 are shifted, dog 35, knob 50a and pin38 are adjusted, and the machine is ready for the automatic cycle.

The valve 81 may also be used in effecting rapid restoration of thewheel slide III to a previous operating position after interruption ofthe automatic cycle. Should it be necessary to withdraw the grindingwheel at any time during the automatic infeed, the operator need onlyshift the valve I3 to its reverse position by means of the rotaryoperating device I3a (Fig. 13) having thereon an eccentric pin l3breceived in a slot in the side of the plunger I3c. Then to restore thewheel to its previous position, the slide need not be advancedstep-by-step in alternation with strokes of the table. Instead, thevalve I3 is shifted manually to its advance position, and when the rapidadvance of the slide has been terminated by tripping of the valve I5,the operator pushes in the valve 81. As previously noted, this connectsline 25 to exhaust so that the slide piston I2 advances rapidly. Whenthe operator observes that the grinding wheel is approached close to itsprevious position, he releases the valve 81. The latter is thrust backout by the biasing pressure from line I8, thereby interrupting theconnection of the line 25 to exhaust, and the system resumes its normalautomatic stepby-step advance of the wheel slide.

Leakage prevention in metering circuit Step-by-step advance of the slideI is, as heretofore described in connection with Figs. 3 and 4,accomplished by metering out successive increments of fluid from theactuator cylinder In via the lines 24, 25 and metering plunger I5. Inthe event that each step of advance is but a few thousandths of an inch,as is the case in a grinding machine, even a small volume of fluidleaked from the metering line or circuit would result in a largepercentage error in the length of the step. Even in instances wherelonger steps are used, precision results depend upon the prevention ofloss of fluid from the metering line.

Examination of the detail of the path of fluid through the meteringcircuit (see Fig. 13) reveals sliding surfaces, along which leakagemight take place, at a number of points, viz.: along the piston I2, thestop bushing II, the plunger I30 of the valve I3, the plunger 26 of thevalve I5, plunger I 411 of the valve I4, the plunger 54a of the pilotvalve 54, and along the metering plunger I6 itself. Even with precisionfitting which should be used for these sliding parts, some leakage wouldtend to occur.

The general plan followed in preventing leakage from the meteringcircuit along the various sliding parts noted is to maintain themetering circuit pressure substantially equal to that in some availablesource of pressure fluid, here the pressure line I8, and applypressure'from the latter at the sliding parts in question in a manner tocounteractany tendency of fluid to flow out of the metering circuitbetween the sliding surfaces and thus to prevent leakage therealong.

To maintain the pressure in the metering circuit equal to that in thepressure line I8, the active faces of the piston I2 and active face ofthe plunger II are suitably dimensioned. This is relatively simple in agrinding machine, diamond boring machine, or the like since the load orresistance to the tool oifered by the work is very uniform as well asbeing substantially ne li iblein comparison with the positioningpressure 14 from the plunger I I. Accordingly, the area of the plungerII is but slightly less than the differential in area between the twofaces of the piston I2, the plunger having been shown as exaggeratedlysmall in the drawings for the sake of clarity. In machines having heavywork resistance, the same can be compensated by dimen= sioning piston I2and plunger II or by making some exterior provision for fluid pressurecontrol. It will be understood, of course, that the reference herein tomaintenance of pressure in line z iedual to that in line I8 has to doonly with the feed portion of the cycle (Figs. 2 and 3), for in rapidapproach the line 24 is exhausted (Fig.

With the pressure in lines I8 and 24 equalized as described, the fluidpressures, that is, the

forces per unit area, on opposite faces of the piston I2 are balanced sothere is no tendency for fluid to leak past it from either and to theother (see Fig. 13). Pressure from line I8,"via line 23, is also appliedto annular interconnected grooves Ila and ill) in the stop bushing I! sothat leakage along it is likewise prevented. In this way leakage offluid trapped in the cylinder Iila on the advancing side of the pistonI2 is prevented and all of it forced to emerge from the cylinder intothe line 24.

Following down the line 24 (Fig. 13) it will be seen that in the valveI3 the valve ports are formed in a stationary sleeve l3d fixed in thecasing I3e and receiving the sliding plunger I30. When the plunger iScis in its upper or advance position shown, a peripheral groove I3therein 1 connects lines 2!: and 25. In the plunger I3c on oppositesidesof the annular passage I3) are transverse. passages, interconnectedby a longitudinal bore 'ifia and to which pressure fluid is suppliedfrom the line I8 through the peripheral annular groove I 3y which alsosupplies fluid to the line 23. The length of the groove I39 insuresregistry of the same with the port of line I8 in either position of thevalve plunger so that pressure is always applied in as, '59 from theline 18.

' Such provision of fluid at 18, I9 equalized in pressure with that inlines 23, 25 efiectually prevents leakage from the latter along thevalve plunger I30.

Similar precautions against leakage are taken in the valves I l, I and54 (see Fig. 13); Thus in the valve I4 the valve plunger Ida is providedwith two peripheral annular grooves Mb and I40 which serve to connectthe lines 36, 3'5 leading from opposite ends of the metering plungercylinder a, respectively, to lines and I9 in alternate positions of thevalve plunger; To guard against the leakage of fluid from the line 25along the valve plunger Ida from either of the passages Mb or I lcpressure fluid from the line I8 is supplied to transverse passages 88 inthe valve plunger through a longitudinal bore BI and an annularperipheral passage 82 in the plunger. ihe latter passage 82 is longenough to register with the port from the line I8 in either of thealternate positions of the plunger Ma;.

and the transverse passages 88, leading to annular peripheral grooves,are located on respective opposite sides of each of the annular passagesI-ib and Me.

In the valve I5 pressure fluid from the line I8 is supplied to oppositesides of the port from line 25 to annular grooves 85 and a surroundingthe valve plunger, on opposite sides of the port from line 25. In thepilot valve 5!! pressure fluidzrl from the line as is directed intoports which,

when the valve plunger is in its left position:

shown, register with annular grooves-'86 located in the valve plungeronopposite sides of the portv leading from the line 2-4;

In the case of the metering; plunger l6 and its associated adjustablestop pin 38, pressure is applied from the line l8 to annular grooves 83and 84 surrounding respective ones of the same to prevent leakage alongthem.

I'claim as my invention:

1. In a hydraulic system: for effecting a stepby-step relative movementof apair of members, the combination of a piston and-cylinder type fluidactuator, means for withdrawing metered increments of fluid from thecylinder to efiect successive steps of advance of the piston within thecylinder, means including a movable stop for intercepting the-advance ofthe piston, means for'adjustably limiting movement of said stop bothtoward and away from the piston in the directionof piston travel, meansfor urging said stop to'its limit of movement toward the piston, andmeans responsive to completionv of the advance ofthe piston forward intojuxtaposition with s'aid'stop for freeing'the stop for movement to itsopposite limit position under the thrust of the piston in asubsequentand final step of advance of the latter, whereby the setting of thelimit positions of the stop by said adjustable limit means determinesthe length of said final step of advance for the piston.

2 The combinationwith a piston and cylinder type actuator, and means forwithdrawin determinate metered increments of, fluidv from the cylinderto effect successive steps of relative advance for the piston: withinthe cylindenof stop means positionable in response .to fluidpressure foradjustably predetermining the length or only the last step inthe series,

3. The vcombination with a piston and cylinder type actuator, and meansfor withdrawingmetered increments. of fluid from the cylinder to effectsuccessive steps of relative advance for the piston within the cylinder,of adjustable stop means positionable in response to fluid pressure forpredetermining the length of the last step in the series and positivelyarresting further advance of the piston upon the completion of said laststep.

4. The combination of a piston and cylinder type actuator, means forsupplying pressure fluid to one side of said piston and forintermittently withdrawing determinate meteredincrements of fluid fromthe cylinder at the opposite side of said piston to effectsuccessivesteps of advance for the piston relative to the. cylinder, adjustablestop means positionablein response to fluid pressure. for predeterminingthe length of the last step in the series and for positively arrestingfurther advance of the piston upon completion of. said last step. andmeans rendered operable upon completion of such last step of advance forautomatically initiating a change in the pressure fluidconnections toeffect an uninterrupted supply of pressure fluid to said'other side ofthe piston and an uninterrupted exhaust of'fluid from said cylinder atsaid one side of the piston to thereby effect a substantially continuousrelative movement of said piston and cylinder in a direction opposite tosaid stepped advance.

5. In a delayed action hydraulic control, the combination with a fluidoperable valve, a pair of fluid'conductors, and means for intermittentlyconnecting alternate ones of said conductors to a source of pressurefluid and the remaining one to exhaust,. of means including; a second.fluid operable valve shiftable alternatively inopposite: directionsfrom-an initial mid-position upon ap-- plication thereto of pressurefluidfromzcorre sponding ones of said conductors for connecting theother or exhausted one of said conductors-in each case tosaid firstvalve.

6. In a delayed action'hydraulic control, the combination with a fluidoperable valve, apair: of fluid conductors, and means forintermittently; connecting alternate ones of said conductors toa sourceof pressure fluid-and theremaining-mneto exhaust, of means operable uponactuation: thereof for establishing a connection-to said .valve;

- fromtheone of said conductors whichlislat the moment of such actuationexhausted and: for: maintaining such connection throughout atl'east. thenext succeeding alternation in' pressure and: exhaust conditionsinsaidconductors.

'7. In a delayed' action hydraulic"controhthe combination of a pair offluidtcon'ductors;means? for intermittently connecting alternate: ones:of; said conductors to a source of pressurev fluid and theremainingone'to exhaust, a; first fluid oper-= able valve, meansincludinga second fluid op'er able valveshiftable'alternately inopposite'dire'ctions from an initial mid-position upon app1icationthereto of pressure fluid from corresponding ones of said' conductorsfor: connec't'ing'the other or exhausted one of said'conductorsin eachcase to said first valve, means for shifting said first valve from afirst position thereof to a second position upon application thereto ofpressure fluid at the next succeeding alternationiof pres-- sure andexhaust in said conductors following a shift of said second valve, andmeans operable in response to shiftof said first valve from said firstto saidsecond position thereof for establishing a connection to saidthird valvefrom the one: ofsaid conductors which isexhausted in saidnext succeeding alternation of pressure and exhaust conditions, wherebypressure fluid will be supplied through the last-mentioned connectiontosaid third valve upon the second succeeding alternation in pressure andexhaust condifions following the shift of said second valve.

8. The combination of a pair of fluid conduc'-= tors, means forintermittently connecting alternate ones of said conductors to a sourceof pressure fluid and the remaining one to exhaust, a fluid operablevalve, and control means operable upon actuation thereof forestablishing a con-' nection to said valve for the supply of pressurefluid thereto for actuating the same from one of said conductors onlyafter two alternations in pressure and exhaust conditions in saidconductors have followed such actuation;

9. In a delayed action hydraulic control, the combination of a membershiftable between alternate limit positions, means defining a fluidpressure chamber for moving said member from one of said limit positionsto the other upon application of fluid pressure to suchchamber, meansdefining, a relief passage for relieving the pressure in said chamber,means including a first fluid operable valve shiftable between alternatepositions for opening and closing said relief passage, a pair of fluidconductors, means for intermittently connecting alternate ones of saidconductors to a source of pressure of fluid and the other to exhaust,means for shifting said first valve to its relief-closing positiomandmeans including a second fluid operable valve shiftable in respectiveopposite directions upon application.

thereto of pressure fluid from corresponding ones of said conductors forconnecting the other of said'conductors to said first valve to applypressure fluid to the latter in a direction to shift the same to itsrelief-opening position upon the next succeeding reversal in exhaust andpressure conditions in said conductors.

10. In a delayed action hydraulic control, the combination of a membershiftable between alternate limit positions, means defining a fluidpressure chamber for moving said member from one limit position to theother upon application of fluid pressure to such chamber, a pair offluid conductors, means for intermittently connecting alternate ones ofsaid conductors to a source of pressure fluid and the other to exhaust,and means operable upon actuation thereof for relieving the pressurewithin said chamber in response to the next succeeding alternation inpressure and exhaust conditions in said conductors following suchactuation.

11. In a delayed action hydraulic control, the combination of a fluidoperable valve, a pair of fluid conductors, means for intermittentlyconnecting alternate ones of said conductors to a source of pressurefluid and the remaining one to exhaust, means including a second fluidoperable valve shiftable alternately in opposite directions from aninitial mid-position upon application thereto of pressure fluid fromcorresponding ones of said conductors for connecting the other orexhausted one of said conductors in each case to said first valve, and athird valve shiftable between alternate positions in which itrespectively connects and disconnects both of said conductors to saidsecond valve.

12. The combination of a movable member, means including a reversiblehydraulic actuator for traversing said member reversely to and fro alonga predetermined path, a movable mechanical stop positionable in responseto fluid pressure and interposed in said path to yieldably intercept themotion of said member in one direct'on along the same, means forautomaticaily initiating a reversal of said actuator in response tointerception of said member by said stop, and means manually operable atwill to disable said reversing means, whereby said actuator continuouslyurges said member against the stop after interception of the member bythe stop, and manually operable means for adjustably varying the strokeof said yieldable stop along said path.

13. In a hydraulic system, the combination of a piston and cylinder typeactuator, a stop member located at one end of said cylinder in positionto intercept the relative advance of the piston toward said one end ofthe cyiinder, means including a pair of rigid abutments for definingrespective limit positions of movement of said stop member axially ofthe cylinder, means for applying pressure fluid to the outer side ofsaid stop member to urge the same into its limit position toward saidpiston, means including a valve for initiating relief of such pressureon said stop member, and means positioned for contact by said pistonupon approach thereof to said stop member for actuating said valve.

lei. In a hydraulic system, the combination of a piston and cylindertype actuator, a stop member located at one end of said cylinder inposilieving said fluid pressure on the stop member in response to thenext succeeding alternation in pressure and exhaust conditions in saidconductors following the opening of said valve by said piston.

15. In combination, an actuator cylinder having a piston slidabletherein with a piston rod projecting from but one face of the piston, astop bushing slidably mounted in the end of said cylinder adjacent theother face of said piston, means including 9. pair of rigid abutmentsengageable with said bushing for limiting its sliding motion axially ofthe cylinder, means for applying pressure fluid to the outer end of saidbushing to urge the same toward said piston, a valve element having astem slidable in said bushing and projecting from the inner end thereofin position to be contacted by said piston as the latter approaches thestop bushing, and means for initiating the relief of said fluid pressureon the stop bushing in response to actuation of said valve element bycontact of the piston with said stem.

16. In a hydraulic system, the combination of a piston and cylinderactuator, means for withdrawing metered increments of fluid from thecylinder to effect a step-by-step relative advance of the piston withinthe cylinder, and means for maintaining during a portion of saidstepby-step advance a substantial equalization of pressure on oppositesides of said piston to prevent the leakage of fluid past the same.

17. In a hydraulic system, the combination of an actuator including apiston and cylinder, a metering device including a plunger and cylinder,means defining an outlet passage from said actuator cylinder to saidmetering cylinder for withdrawal from the actuator cylinder of a meteredincrement of fluid corresponding to the displacement shift of saidmetering plunger upon each stroke of the latter, and means formaintaining during withdrawal of said metered increment of fluid asubstantial equalization of pressures on opposite sides of said pistonas well as for applying fluid to the periphery of the plungerintermediate its ends at a pressure substantially equal to that of thefluid entering said metering cylinder from said actuator cylinder.

18. In a hydraulic system, the combination of minate successiveincrements of fluid, a movable valve element. interposed in saidpassage, and

means for applying to said valve element fluid under a pressuresubstantially equal to that in said passage and such application beingat plural REFERENCES CITED The following referencesareof record in the;file' of this' patent:

UNITED STATES PATENTS Number Name Date 448,277 Ta-ylor Mar. 17, 1891,526,930 Maxon Oct. 2, 1894 637,461 Hartness Nov. 21,v 1-899 Number 639651,502 882,889

20 Name Date; Leavitt ;Dec,. :26, 18992 Fitzgeraildau \June'1'2,.190.0'Hoxie Mar. 4, le9fi8 Heald Apr; "257', 1926- La ussucq; 3:926: ErnstAug. 25",-.1'93if Speck Sept. 15932 Ernst Apr; 156,1 9.35-Maglottkfluuuu- Aug. 23 .1933 Keel May -9, H1939. Daugherty Oct. :31,.1949 :DBJViS' 53711.. 5?;13945 Waldie Feb. 5;, 19k?!

